The present invention relates in general to spring elements, and, more particularly, to a spring element for use in an apparatus for attaching to a plurality of contacts of a semiconductor.
Unpackaged or bare semiconductor dies are used to construct multi-chip modules (MCMs) and other electronic devices. Unpackaged dies must be tested and burned in during the manufacturing process to certify each die as a known good die. This has led to the development of temporary packages that hold a single bare die for testing and burn-in. The temporary packages provide the electrical interconnection between the test pads on the die and external test circuitry. Exemplary temporary packages are disclosed in U.S. Pat. Nos. 5,302,891, 5,408,190 and 5,495,179 to Wood et al., which are herein incorporated by reference.
Typically, this type of temporary package includes an interconnect having contact members that make a temporary electrical connection with the test pads on the die. The temporary package can also include an attachment device that presses the die against the interconnect. The attachment device may include a clamping device that attaches to a package base and a spring element that presses the die against the interconnect. The configuration of the spring element is dependent on a number of factors. The spring element must be able to withstand relatively high compressive forces and relatively high burn-in temperatures without experiencing compression set. Further, the dimensions of the spring element must be such that it is compatible with the temporary package. Finally, the spring element must be able to withstand the amount of pressure required for pressing the die against the interconnect without causing an excessive amount of force to be transferred to the die, and thus damaging the same.
Springs elements used in the prior art are typically formed using rubber-like materials, such as silicone. Such springs elements are poor conductors of heat and electricity which limits the applications in which they can be used. It would be desirable to have a spring element which was electrically conductive for backside biasing of the semiconductor being tested. It would also be desirable to have a spring element which had improved thermal conduction properties for those applications in which increased heat dissipation is necessary.
Accordingly, there is a need for a spring element which is compatible with the temporary packages and environment used to test and burn-in semiconductors. There is also a need for a spring element which has improved thermal and electrical conduction properties. Preferably, such spring elements would be reusable and inexpensive to manufacture.
The present invention meets this need by providing a spring element having a modulus of elasticity which may be adjusted according to the required environment. Metallic particles or films may be added to the spring element to increase its thermal and electrical conduction properties. The spring element may be wrapped in a metallized woven fabric and mechanically clamped to the cover of the semiconductor testing device, thereby alleviating the need for a load distributing pressure plate. Material may be removed from or added to the spring element to change the modulus of elasticity as needed. The shape of the spring element may also be varied to change the modulus of elasticity, the spring constant, and the force transfer capabilities of the spring element.
According to a first aspect of the present invention, a spring element comprises a first elastic member and a conductive member. The first elastic member is comprised of a first elastomeric material having a first modulus of elasticity. A portion of the first elastomeric material is removed from the first elastic member such that the spring element has an overall modulus of elasticity different from the first modulus of elasticity.
The portion of the first elastomeric material removed from the first elastic member may form a hole in the first elastic member. Preferably, the first elastic member is o-ring shaped. The first elastic member may also comprise a plurality of holes. The spring element may further comprise a second elastic member comprised of a second elastomeric material having a second modulus of elasticity, with the second elastic member being positioned in at least one of the plurality of holes formed in the first elastic member such that the overall modulus of elasticity is different from the first and second moduli of elasticity. The spring element may further comprise a plurality of the second elastic members with the plurality of the second elastic members being positioned in a plurality of the plurality of holes in the first elastic member. The portion of the first elastomeric material removed from the first elastic member may form a cavity in the first elastic member. Preferably, the first elastic member includes a plurality of cavities formed therein.
The conductive member may comprise a plurality of conductive particles. Preferably, the plurality of conductive particles are interspersed within the first elastic member. Alternatively, the conductive member may comprise a layer of conductive material formed over the first elastic member or a plurality of conductive threads. The plurality of conductive threads may comprise a plurality of non-conductive threads having a conductive coating. Preferably, the plurality of conductive threads form a covering around the first elastic member. The conductive member may be comprised of conductive material selected from the group consisting of gold, aluminum, nickel, silver stainless steel, and alloys thereof. The conductive member may also be comprised of carbon.
According to another aspect of the present invention, a spring element comprises a first elastic member, a second elastic member and a conductive member. The first elastic member is comprised of a first elastomeric material having a first modulus of elasticity and the second elastic member is comprised of a second elastomeric material having a second modulus of elasticity. The second elastic member is positioned within the first elastic member such that the spring element has an overall modulus of elasticity different from the first: and second moduli of elasticity.
The spring element may further comprise a plurality of the second elastic members positioned within the first elastic member. The conductive member may comprise a plurality of conductive particles, a layer of conductive material formed over the first elastic member, or a plurality of conductive threads.
According to a further aspect of the present invention, a spring element comprises a plurality of interwoven threads and a conductive member. The conductive member may comprise a plurality of conductive particles, a layer of conductive material formed over the first elastic member, or a plurality of conductive threads. Preferably, the plurality of conductive threads are interwoven with the plurality of interwoven threads.
According to yet another aspect of the present invention, a spring element comprises a conductive member and an elastic member having a variable spring constant. The conductive member may comprise a plurality of conductive particles, a layer of conductive material formed over the first elastic member, or a plurality of conductive threads.
According to another aspect of the present invention, an apparatus for attaching to a plurality of contacts of a semiconductor comprises an interconnect structure comprising a plurality of conductors patterned to match corresponding ones of the plurality of contacts of the semiconductor and an attachment device pressing the interconnect structure against the semiconductor to provide an electrical connection between the plurality of conductors and the corresponding ones of the plurality of contacts. The attachment device comprises a spring element including an elastomeric member and a conductive member.
The conductive member may comprise a plurality of conductive particles. Preferably, the plurality of conductive particles are interspersed within the first elastic member. Alternatively, the conductive member may comprise a layer of conductive material formed over the first elastic member or a plurality of conductive threads. The plurality of conductive threads may comprise a plurality of non-conductive threads having a conductive coating. Preferably, the plurality of conductive threads form a covering around the first elastic member. Preferably, the conductive member is comprised of conductive material selected from the group consisting of gold, aluminum, nickel, silver, stainless steel, and alloys thereof. The conductive member may also be comprised of carbon.
The semiconductor may be electrically biased through the spring element. The semiconductor may comprise a semiconductor die. The semiconductor may comprise a semiconductor die formed within a semiconductor package. The semiconductor package may comprise a package selected from the group consisting of a chip-scale package, a ball grid array, a chip-on-board, a direct chip attach, and a flip-chip.
According to yet another aspect of the present invention, an apparatus for attaching to a plurality of contacts of a semiconductor comprises an interconnect structure comprising a plurality of conductors patterned to match corresponding ones of the plurality of contacts of the semiconductor and an attachment device pressing the interconnect structure against the semiconductor to provide an electrical connection between the plurality of conductors and the corresponding ones of the plurality of contacts. The attachment device comprises a cover and a spring element mechanically coupled to the cover. The spring element comprises an elastomeric member and a plurality of conductive threads forming a covering over the spring element.
The cover may comprise a first clamping member configured so that a first end portion of the spring element is force fit to the cover. The cover may further comprise a second clamping member configured so that a second end portion of the spring element is force fit to the cover.
According to a further aspect of the present invention, an apparatus for attaching to a plurality of contacts of a semiconductor comprises an interconnect structure comprising a plurality of conductors patterned to match corresponding ones of the plurality of contacts of the semiconductor and an attachment device pressing the interconnect structure against the semiconductor to provide an electrical connection between the plurality of conductors and the corresponding ones of the plurality of contacts. The attachment device comprises a spring element including a conductive member and a first elastic member comprised of a first elastomeric material having a first modulus of elasticity. The first elastic member includes a plurality of holes formed therein such that the spring element has an overall modulus of elasticity different from the first modulus of elasticity.
According to a still further aspect of the present invention, an apparatus for attaching to a plurality of contacts of a semiconductor comprises an interconnect structure comprising a plurality of conductors patterned to match corresponding ones of the plurality of contacts of the semiconductor and an attachment device pressing the interconnect structure against the semiconductor to provide an electrical connection between the plurality of conductors and the corresponding ones of the plurality of contacts. The attachment device comprises a spring element including an elastic member comprised of a conductive member and an elastomeric material having a modulus of elasticity. The elastic member includes a hole formed therein such that the spring element has an overall modulus of elasticity different from the modulus of elasticity of the elastomeric material. The elastic member is shaped so as to engage an outer edge of the semiconductor such that a force applied by the attachment device as the interconnect structure is pressed against the semiconductor is substantially uniform around the semiconductor.
According to yet a still further aspect of the present invention, an apparatus for attaching to a plurality of contacts of a semiconductor comprises an interconnect structure comprising a plurality of conductors patterned to match corresponding ones of the plurality of contacts of the semiconductor and an attachment device pressing the interconnect structure against the semiconductor to provide an electrical connection between the plurality of conductors and the corresponding ones of the plurality of contacts. The attachment device comprises a spring element including a first elastic member, a second elastic member and a conductive member. The first elastic member comprises a first elastomeric material having a first modulus of elasticity and the second elastic member comprises a second elastomeric material having a second modulus of elasticity. The second elastic member is positioned within the first elastic member such that the spring element has an overall modulus of elasticity different from the first and second moduli of elasticity.
According to another aspect of the present invention, an apparatus for attaching to a plurality of contacts of a semiconductor comprises an interconnect structure comprising a plurality of conductors patterned to match corresponding ones of the plurality of contacts on the semiconductor and an attachment device pressing the interconnect structure against the semiconductor to provide an electrical connection between the plurality of conductors and the corresponding ones of the plurality of contacts. The attachment device comprises a spring element comprised of a plurality of interwoven threads and a conductive member.
According to yet another aspect of the present invention, an apparatus for attaching to a plurality of contacts of a semiconductor comprises an interconnect structure comprising a plurality of conductors patterned to match corresponding ones of the plurality of contacts of the semiconductor and an attachment device pressing the interconnect structure against the semiconductor to provide an electrical connection between the plurality of conductors and the corresponding ones of the plurality of contacts. The attachment device comprises a spring element including a conductive member and an elastic member comprised of an elastomeric material having a modulus of elasticity. The elastic member includes at least one cavity formed therein such that the spring element has an overall modulus of elasticity different from the modulus of elasticity of the elastomeric material.
According to a further aspect of the present invention, an apparatus for attaching to a plurality of contacts of a semiconductor comprises an interconnect structure comprising a plurality of conductors patterned to match corresponding ones of the plurality of contacts of the semiconductor and an attachment device pressing the interconnect structure against the semiconductor to provide an electrical connection between the plurality of conductors and the corresponding ones of the plurality of contacts. The attachment device comprises a spring element including a conductive member and an elastic member having a variable spring constant
Accordingly, it is an object of the present invention to provide a spring element which is compatible with the temporary packages and environment used to test and burn-in semiconductors. It is another object of the present invention to provide a spring element which has improved thermal and electrical conduction properties. It is another object of the present invention to provide a spring element which is reusable and inexpensive to manufacture. Other features and advantages of the invention will be apparent from the following description, the accompanying drawings, and the appended claims.